New research suggests that Earth-like worlds with similar land-to-ocean ratios to our planet’s may be exceedingly rare. Thus, it turns out that the search for habitable worlds should look for dry, cold “pale yellow dots” instead of “pale blue dots” like Earth, as once described by astronomer Carl Sagan.
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Planetary scientists Tilman Spohn and Dennis Höning studied possible exoplanets to see how evolutions and cycles of continents and water could shape the development of habitable exoplanets. The findings of the study were presented at the Europlanet Science Congress 2022 in Granada.
According to the pair, planets have an 80 percent chance of having mostly land-covered surfaces. In other words, they would resemble “pale yellow dots” and have mostly continental landscapes. They also discovered that 19 percent of potentially habitable worlds would probably have oceans. Meanwhile, less than one percent would have a land-water ratio similar to Earth’s with “pale blue surfaces” when observed from afar.
“We Earthlings enjoy the balance between land areas and oceans on our home planet. It is tempting to assume that a second Earth would be just like ours. But our modeling results suggest that this is not likely to be the case,” Spohn, Executive Director of the International Space Science Institute in Switzerland, said in a statement.
The study found that ocean exoplanets, with less than 10 percent land, could turn out to be moist, warm planets. Those temperatures might be similar to Earth’s after it recovered from the asteroid impact that caused the extinction of the dinosaurs. So, such worlds could be teeming with life forms.
Planets with less than 30 percent oceans, on the other hand, would have colder temperatures and dryer climates. The planets might also have cool deserts and possibly some ice sheets. And we know from similar regions here on Earth that life also thrives in such environments.
Earth keeps evolving and looks different from how it was at various stages in history. For instance, over a billion years ago, all landmasses on Earth were all joined into one gigantic continent before splinting into six continents as it is today. Thus, it’s possible there are exoplanets with climate conditions similar to those our planet endured during the Ice Ages, according to Spohn and Höning.
This study shows the way for scientists who are searching for life in the cosmos, as instead of looking for a “pale blue dot”, they should be searching habitable zones for “pale yellow dots.”